OLED display devices have been developed rapidly in recent years due to superior properties such as wide color gamut, the high contrast ratio and so on, which are more and more competitive in the display realm. The conventional OLED display devices basically adopt the active driving manner. As the organic light-emitting diode is a current device, precise control of the current has been a critical consideration.
The conventional pixel compensation circuit consists of two thin film transistors and a memory capacitor, as shown in FIG. 1. The pixel compensation circuit includes a controllable switch T1, a driving switch T2 and a memory capacitor C1. The driving current of the organic light-emitting diode D1 is controlled by the driving switch T2, the current thereof is IOLED=k(Vgs−Vth)2, where k is a current amplification coefficient of the driving switch T2, which is determined by the inherent property of the driving switch T2, Vth is a threshold voltage of the driving switch T2. As the threshold voltage Vth of the driving switch T2 can easily shift, the organic light-emitting diode D1 drives the current to be changed, which leads to the brightness of the OLED display device to be uneven, further affecting image quality.